The broad long-term objective of the present series of studies is to investigate speech motor control in children from a developmental perspective. Data will be collected from children using a mixed- longitudinal design. Respiratory and laryngeal kinematic data will be collected while children and adults speak normally, and at a loud vocal intensity level. Collection of respiratory data will initially evaluate alternative transduction systems - linearized magnetometers and Respigraph. Laryngeal data will be collected with an electroglottograph and pneumotachograph: the electroglottographic waveform will be interpreted in conjunction with the inverse-filtered glottal airflow waveform. Dependent measures for respiration include per cent vital capacity used, maximum end-inspiratory level, and maximum end-expiratory level. Descriptions of the relative contribution of the rib cage and abdomen will be made for individual subjects. Dependent measures for laryngeal movement include open quotient, closed quotient and slope of the closing portion of the electroglottograph waveform. Variability of these data will be studied and interpretations about speech motor control will be made. Finally, a methodological study will be conducted to determine whether linearized magnetometers or Respigraph will be more efficient for sensing respiratory kinematics in children, and to determine whether the two devices will yield similar measures. The specific research questions are as follows: (a) At what age/s do children begin to use a similar respiratory-laryngeal mechanism as adults to vary vocal intensity? (b) What is the nature of the respiratory mechanism that is used by children? (c) Do children use a laryngeal mechanism when increasing their vocal intensity? (d) Are children's respiratory and laryngeal movement data more variable from each other depending on age and are children as a group more variable than adults? (e) What is the most efficient sensing device for measuring respiratory kinematics in children? Data will contribute to the establishment of a developmental model of speech motor control and provide a valid functionally informed basis for treating disordered speech motor control in children.